Implantable medical devices are available for monitoring physiological signals in a patient. For example, a patient's blood pressure signal may be monitored using a pressure sensor typically mounted along a transvenous lead and advanced to a desired monitoring location. A pressure sensor may be positioned within a ventricular or atrial chamber or along a vein or artery for monitoring for physiological events that influence the blood pressure signal or relate to the hemodynamic status of the patient. Pressure sensor signals contain artifact due to mechanical noise, such as bumping of the pressure sensor against anatomical structures, movement caused by coughing or other respiratory maneuvers, or other movement. This signal artifact may fall within the frequency range of the desired signal properties used for monitoring the patient. As such, artifact removal using conventional filtering or other signal averaging methods may not be effective in removing the artifact without losing desired signal information. Apparatus and methods are needed, therefore, for distinguishing physiological sensor signal waveforms contaminated by artifact from waveforms that do not contain artifact to allow accurate and reliable monitoring of the patient.